(1) Field of the Invention
The present invention relates to a molding device for flat plug, more particularly to one allows precise and rapid holding of flexible wires in position during the process of injection molding.
(2) Description of Prior Art
Flat plug gives highly practical use for space-saving and less vulnerable to be pulled out by accident due to the lead-out direction of the conductor wires is vertical to that of the plug blades. However, there exists certain difficulty in the injection molding of flat plug, that is, how to achieve precise positioning of the flexible conductor wires within a limited height of the mold cavity in the process of injection molding of flat plug so that the wires when molded will not be exposed due to displacement in the molding becomes crucial in the molding technology. FIGS. 9 and 10 illustrate the molding methods for the prior art of flat plug, within, thin and rigid forks or blades are used to provide support and fixing by clamping the flexible conductor wires at the precise location inside the mold cavity in the process of injection molding; furthermore, such forks or blades will retract during the final filling stage of molding to allow the plastics back flow into the cave left by the retracted blades, or blades may be retracted upon completing the injection cycle and leave a hollow on the molded workpiece while said forks or blades are made as thin as possible. However, the forks or blades when made thin fail to sufficient rigidity required by precise positioning of the flexible conductor wires at ideal location. Therefore, a practical modification involves retaining said blades in the cast dies and being extruded when the molding plastics get condensed and hardened while leaving a very small and thin hollow on said molded workpiece, such a hollow though causing insignificant affects upon the structure of the molded workpiece, affects the appearance of the finished product by leaving dents on its surface. In addition, said modified molding requires that the conductor wires to be placed in the semi-mold cavity of the lower die before being put in position with said forks or blades, and plastics molded workpiece are filled through injection fluid lateral duct in conjunction the counter locked dies. An issue of manufacturing speed exists, i.e., the prior art must pass through the following procedures in the entire injection molding process:
1. Installing the components into the cavity--plug blades and flexible conductor wires are placed in the cavity of the lower die before both of upper and lower dies are closed, with the plug blade leading through and out from the preserved hole at the lower cavity and the flexible conductor wires following their preset routes are inhibited one by one at the grip ends of said forks (or blades); in case of longer preset routes, the number of said forks increases accordingly, meaning, it consumes more time for the flexible conductor wires to mutually hold in place with the grip ends of each fork to achieve the precise positioning for the wires within a limited height of the cavity. PA0 2. Closing dies--both upper and lower dies close on to each other. PA0 3. Injection--hot melting plastics are injected, cooled and solidified in the cavities when the forks may retreat from or stay in the cavities at the final stage of this stage. PA0 4. Opening dies--both upper and lower dies are opened up, then the already solidified plastics wall wrap up the components placed in Step 1 and the finished product is availed once entirely removed from the cavities for the mold to place another set of components to commence the next cycle of injection molding. PA0 1. in case of harder plastics--they may provide better strength for the flat plug, proper flexibility to the connection between the plug end and the power line is prevented; and routing for the power wire at such connection will lack in mobility, thus fails to meet requirements of various working environment in practice when such connection end gets too hard. PA0 2. in case of softer plastics--proper flexibility to the connection end is possible but at the expense of proper strength to the flat plug, which then becomes very vulnerable to deformation when external force is applied(e.g., plug is pulled off), and repeated deformation means contacts of conductor wire inside the plug can easily be disengaged or show poor contact, resulting in electric shock or fire hazard. PA0 3. in case of non heat-withstanding plastics--several home appliances consume larger amperage, such as electric iron, and the plug itself gets hotter and softer, leading to deformed plug or accident. PA0 4. in case of plastics meeting all requirements as aforesaid--even there is a type of plastics that is with ideal hardness, fire-proof, and heat-withstanding available for injection molding, the higher cost of such a material is bad news to market competition.
Judging from the procedures disclosed above, it is easy to know that the first step of the prior art requires the process to be operated only during both upper and lower dies are opened up. If the opening and closing of both upper and lower dies are automatically controlled(opened/closed at given time), the operator would have to complete Step 1 within a limited time, and if any fork fails to accurately grip the flexible conductor wires, such section of wire may be exposed due to displacement in the course of filling, resulting in defective product. Furthermore, if the opening/closing of both upper and lower dies are manually controlled, Step 2 will be entered only upon the completion of Step 1 at the cost of the control of output since the time consumed in Step 1 differs. Also, the operator will have to wait out Steps 2 and 3 resulting in a less optimal use of manpower.
The prior art of molding process for allowing only one type of plastics for hot melting injection fails to meet those functional requirements of individual applications, namely:
Flat plugs using the prior art of injection molding have less changes to the appearance of the finished products, more difficulties in the demonstration of product quality or special appeal, and less diversified and capable of meeting the individual demands on style among customers.